1. Field of the Invention
The present invention relates to increasing the performance of aircraft and, more particularly, to an apparatus and method for increasing the angle of attack operating range of an aircraft.
2. Description of the Related Art
When aircraft wings stall due to flow separation, roll control devices such as conventional ailerons or spoilers become ineffective. By increasing the angle of attack operating range over which aircraft aerodynamic roll control surfaces are effective, maneuverability is enhanced, the aircraft can fly slower, and it may utilize shorter runways.
U.S. Pat. No. 3,152,775 issued to J. A. Boyd, entitled "SUPERSONIC AIRCRAFT", discloses movable control surfaces carried by the wing tips for providing roll control for the aircraft. The movable control surfaces are shown in a generally vertical orientation relative to the wing. Thus, although deriving benefits for supersonic aircraft, the Boyd invention would not serve to allow an increase in the angle of attack.
U.S. Pat. No. 4,247,062, issued to H. Brueckner, entitled "HIGH EFFICIENCY VERTICAL TAIL ASSEMBLY COMBINED WITH A VARIABLE WING GEOMETRY", discloses a vertical tail unit combined with a variable wing geometry for large angles of attack. The vertical tail unit is hinged for adjustment about an axis substantially parallel to the longitudinal axis of the fuselage. The outer wing portions are connected, at an angle, with a vertical tail unit which is directed vertically downward in its normal position. The Brueckner, et al. reference does not provide for directional (roll) control.
U.S. Pat. No. 3,025,027, issued to P. F. Ferreira, entitled "VERTICAL AIRFOIL" discloses an aircraft using three vertical airfoils for enhancing lift. The vertical airfoils produce a lifting force the sum of which is located substantially over the center of gravity of the aircraft.
U.S. Pat. No. 3,826,448, issued to S. M. Burk, Jr., entitled "DEPLOYABLE FLEXIBLE VENTRAL FINS FOR USE AS AN EMERGENCY SPIN-RECOVERY DEVICE IN AIRCRAFT", discloses a flexible fin device for mounting to an aircraft to affect spin recovery. The device may be selectively deployed to provide a triangular platform of flexible material to provide spin recovery, and retracted for compact storage during non-use. A single flexible fin may be deflected in a specific direction depending on direction of the spin rotation, or two flexible fins forming an inverted "V" configuration may be used according to the invention. The device is mounted on the underbody of the aircraft.
U.S. Pat. No. 3,845,918 issued to R. P. White, Jr., entitled "VORTEX DISSIPATOR" discloses the use of a fixed plate secured to the tip of an airfoil and aligned with the free stream direction. The plate extends forward from the trailing edge of the tip and outward from the section side of the lifting surface and is configured so that the resultant of the velocity of the free stream flow and the rotational velocity of the vortex produces a stall angle of attack relative to the plate and dissipates much of the strength of the vortex.
U.S. Pat. No. 3,834,654, issued to L. R. Miranda, entitled "BOXPLANE WING AND AIRCRAFT" discloses an aircraft wing system wherein a first pair of rearwardly swept wings is interconnected at the wing tips to a second pair of forwardly swept wings, the interconnection being accomplished by a pair of vertically swept fins. The two pair of wings are horizontally and vertically staggered relative to one another. Each pair of wings is also structurally attached to another aircraft component.